FM multiplex broadcasting receiver and storage of received data in FM multiplex broadcasting receiver

ABSTRACT

A prefix corresponding to a data block at the head of each of data groups in data of a layer  3  of a received FM multiplex broadcast program and data of a layer  4  of the received FM multiplex broadcast program are stored in first storage means. When a data retention command is entered, the data of the layer  3  is produced on the basis of the prefix and the data of the layer  4  which are stored in the first storage means, and the produced data of the layer  3  is retained in second storage means as versatile recording and reproducing data.

TECHNICAL FIELD

The present invention relates to an FM multiplex broadcasting receiverand a method of retaining received data in the FM multiplex broadcastingreceiver.

BACKGROUND ART

FM multiplex broadcasting is for broadcasting voices, characters,figures together with stereo voices, that is, one for multiplexingvoices, characters and figures on normal FM broadcasting andbroadcasting the multiplexed voices, characters and figures.

Typical examples of the standard of the FM multiplex broadcastinginclude three systems, that is, DARC (Data Radio Channel), a fixedreceiving system, and RDS (Radio Data System). The DARC is the newest,and is employed as an international standard. The DARC is described inaccordance with “Reference Model of Data Broadcasting” in Recommendation807 of ITU-R (International Telecommunication Union).

The DARC is for converting characters and figures into digitalinformation, modulating a sub-carrier frequency of 76 kHz andfrequency-multiplexing the sub-carrier frequency on a stereo base bandsignal, frequency-modulating the multiplexed signal, and broadcastingthe frequency-modulated multiplexed signal.

FIG. 6 illustrates a layer structure representing a character/figurecoding system of the DARC.

A layer 1 specifies transmission path characteristics. A sub-carriersignal is superimposed on the side of higher frequencies than those ofan L+R signal and an L−R signal which are normal FM stereo broadcastingsignals. Modulation method of sub-carrier employs an LMSK(Level-controlled Minimum Shift Keying) method for controlling the levelof a sub-carrier by the degree of modulation of the L−R signal inconsideration of the fact that the interference of the sub-carrier witha voice signal becomes significant when the degree of voice modulationis small.

A layer 2 defines a frame structure of data including anerror-correcting system. Each of frames is composed of 272 blocks in thecolumn direction, and a 16-bit block identification code (BIC) is addedto the head thereof. Frame synchronization and block synchronization areachieved on the basis of the block identification code. 190 blocks outof the 272 blocks in the column direction are a packet for transmittingdata, and 82 blocks are a parity packet for transmitting a parity in thevertical direction. Each of the packets is composed of a 176-bit dataportion, 14-bit CRC (Cyclic Redundancy Code) which is an error-detectingcode and a 82-bit horizontal parity portion in the row direction.

Transmitted data is first subjected to error correction in a step of thelayer 2 with its one frame as a basic unit. In practice, the transmitteddata is sent out in a frame structure in which packets and paritypackets are arranged again in a predetermined order in the longitudinaldirection, as shown in FIG. 7.

A layer 3 defines the structure of a data packet. The data packet iscomposed of 176 bits excluding BIC, CRC and a parity in each row in aframe. The data packet is composed of a prefix and a data block.

A layer 4 indicates the structure of a data group. The data group iscomposed of one or a plurality of data blocks. The data group alsoincludes CRC which is an error-detecting code. The transmitted data isalso subjected to error detection in the layer 4. One of the data groupscorresponds to data on one page.

A layer 5 defines the structure of a bundle of information transmittedby FM multiplex broadcasting, that is, program data.

FIG. 8 illustrates using functional blocks the schematic construction ofan FM multiplex broadcasting receiver utilizing a personal computer.

The FM multiplex broadcasting receiver comprises a tuner 301, asub-carrier data receiving LSI302 a receiving processing unit 303, aprogram reconstructing unit 304, a program analyzing unit 305, a displayprocessing unit 306, a plotting unit 307, and a display 308. In an FMmultiplex broadcasting receiver utilizing a personal computer, the tuner301, the sub-carrier data receiving LSI 302, and the receivingprocessing unit 303 are constituted by a PC card or the like. Further,the program reconstructing unit 304, the program analyzing unit 305, thedisplay processing unit 306, the plotting unit 307, and the display 308are constituted by the personal computer.

The sub-carrier data receiving LSI 302 performs LMSK demodulation anderror correction on the basis of an output from the tuner 301. In thesub-carrier data receiving LSI 302, signals of a layer 1 is convertedinto data of a layer 2.

The receiving processing unit 303 accepts required ones of data in blockunits outputted from the LSI 302. In the receiving processing unit 303,the data of the layer 2 is converted into data of a layer 3.

The program reconstructing unit 304 reconstructs a program. In theprogram reconstructing unit 304, the data of the layer 3 is convertedinto data of a layer 4.

The program analyzing unit 305 performs decoding processing conformingto an eight level coding system. In the program analyzing unit 305, thedata of the layer 4 is converted into data of a layer 6 (the eight-bitcoding system).

The display processing unit 306 acquires a plotting pattern, andsubjects the plotting pattern to various types of processing. Theplotting unit 307 outputs the plotting pattern obtained by the displayprocessing unit 306 to the display 308.

In the FM multiplex broadcasting receiver, examples of a method ofretaining a received program in a data format which can be versatilyrecorded and reproduced include a method of retaining text data obtainedby the program analyzing unit 305 and a method of retaining bit map dataobtained by the display processing unit 306.

When the received program is stored in a text format or a bit mapformat, information representing the hierarchical structure of theprogram, selection of the program, a plotting operation, and the likecannot be retained, whereby the original program at the time ofreceiving cannot be faithfully reproduced.

Therefore, it is considered that only the data of the layer 4 obtainedby the program reconstructing unit 304 is retained. When only the dataof the layer 4 is stored, however, there is no prefix including datarepresenting service identification or the like, whereby the originalprogram at the time of receiving cannot be faithfully reproduced. In theFM multiplex broadcasting receiver, when the data of the layer 4 isretained in a RAM, it is retained in the RAM in its own method such thatthe prefix is reflected. A system for storing the data of the layer 4 inthe RAM is not standardized in all FM multiplex broadcasting receivers.

An object of the present invention is to provide an FM multiplexbroadcasting receiver capable of retaining a received program in such adata format that the original program at the time of receiving can befaithfully reproduced by various types of applications for reproducingFM multiplex broadcasting and a method of retaining received data in theFM multiplex broadcasting receiver.

DISCLOSURE OF INVENTION

An FM multiplex broadcasting receiver according to the present inventionis characterized by comprising means for storing in first storage meansa prefix corresponding to a data block at the head of each of datagroups of a received FM multiplex broadcast program and data of a layer4 of the received FM multiplex broadcast program, an input device forentering a data retention command, and means for producing the data ofthe layer 3 on the basis of the prefix and the data of the layer 4 whichare stored in the first storage means when the data retention command isentered and retaining in second storage means the produced data of thelayer 3 as versatile recording and reproducing data.

The first storage means and the second storage means may be the samestorage device.

A method of retaining received data in an FM multiplex broadcastingreceiver according to the present invention is characterized bycomprising the steps of storing in first storage means a prefixcorresponding to a data block at the head of each of data groups of areceived FM multiplex broadcast program and data of a layer 4 of thereceived FM multiplex broadcast program, and producing the data of thelayer 3 on the basis of the prefix and the data of the layer 4 which arestored in the first storage means when a data retention command isentered and retaining in second storage means the produced data of thelayer 3 as versatile recording and reproducing data.

The first storage means and the second storage means may be the samestorage device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram functionally showing the schematicconstruction of an FM multiplex broadcasting receiver;

FIG. 2 is a schematic view showing the structure of a data packet in alayer 3;

FIG. 3 is a perspective view showing the appearance of the FM multiplexbroadcasting receiver;

FIG. 4 is a block diagram functionally showing the electricalconstruction of the FM multiplex broadcasting receiver;

FIG. 5 is a flow chart showing the procedure for data retainingprocessing in a CPU 40;

FIG. 6 is a schematic view showing the hierarchical structurerepresenting a character/figure coding system of DARC;

FIG. 7 is a schematic view showing the frame structure of DARC; and

FIG. 8 is a block diagram functionally showing the construction of aconventional FM multiplex broadcasting receiver.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to FIGS. 1 to 5, an embodiment in a case where the presentinvention is applied to an FM multiplex broadcasting receiver utilizinga personal computer.

FIG. 1 functionally illustrates the schematic construction of an FMmultiplex broadcasting receiver utilizing a personal computer. In FIG.1, components corresponding to ones shown in FIG. 8 are assigned thesame reference numerals. Data of a layer 4 which is obtained by aprogram reconstructing unit 304 is stored in a storage device 44 in thepersonal computer (see FIG. 4). In the FM multiplex broadcastingreceiver, a prefix corresponding to a data block at the head of each ofdata groups in data of a layer 3 which is obtained by a receivingprocessing unit 303 is also stored in the storage device 44 in thepersonal computer (see FIG. 4), unlike the conventional FM multiplexbroadcasting receiver.

When a received FM multiplex broadcast program is stored in a dataformat which can be versatily recorded and reproduced, the data of thelayer 4 is converted into the data of the layer 3 by a layer 3converting unit 311. The obtained data of the layer 3 is retained asversatile data in the storage device 44 in the personal computer by aversatile data retaining unit 312. The layer 3 converting unit 311converts the data of the layer 4 which is stored in the storage device44 into the data of the layer 3 on the basis of the prefix correspondingto the data block at the head of each of the data groups which is storedin the storage device 44.

The prefix corresponding to each of the data blocks in the layer 3comprises a service identification code for identifying the programcontents (general information, traffic information, additionalinformation, auxiliary information, and an operating signal), a decodingidentification flag, an information termination flag, an update flag, adata group number and a data packet number, as shown in FIG. 2. Theprefix corresponding to each of the data blocks is reproduced on thebasis of the prefix corresponding to the data block at the head of eachof the data groups.

Specifically, the service identification code, the decodingidentification flag, the update flag and the data group number are thesame in one data group. Therefore, the information corresponding to eachof the data blocks are the same as the information in the prefixcorresponding to the data block at the head of each of the data groups.Further, the information termination flag is set to one only in thefinal packet. The data packet numbers are assigned in ascending order tothe data blocks with the data packet number assigned to the data blockat the head of the data group appearing first.

FIG. 3 illustrates the appearance of an FM multiplex broadcastingreceiver utilizing a personal computer.

The FM multiplex broadcasting receiver comprises a notebook-sizedpersonal computer 101, a PC card 102 constituting an FM multiplexdecoding unit 15 as described later (corresponding to the sub-carrierdata receiving LSI 302 and the receiving processing unit 303 in FIG. 1),and a tuner unit 103 constituting an FM tuner unit 14 as described later(corresponding to the tuner 301 in FIG. 1).

The notebook-sized personal computer 101 has the functions of theprogram reconstructing unit 304, a program analyzing unit 305, a displayprocessing unit 306, a plotting unit 307, a display 308, the layer 3converting unit 311, and the versatile data retaining unit 312 byinstalling particular software therein.

FIG. 4 illustrates the electrical construction of the FM multiplexbroadcasting receiver.

An FM multiplex broadcasting signal received by an antenna 12 is sent toan FM demodulating circuit 2 in the FM tuner unit 14. The FM multiplexbroadcasting signal sent to the FM demodulating circuit 2 is subjectedto synchronous detection by local oscillatory wave outputted from a PLLcircuit 4, and is then outputted to the sub-carrier data decoding unit15 through a buffer 6.

The signal inputted to the sub-carrier data decoding unit 15 is sent toa band-pass filter 18 through a buffer circuit 8. In the band-passfilter 18, a signal component in a predetermined frequency band is takenout. An output of the band-pass filter 18 is sent to a demodulation LSI20, so that LMSK demodulation, synchronous detection and errorcorrection are performed.

A CPU 26 reads out received data from the demodulation LSI 20 uponreceipt of a data transfer request issued for each 18 msec from thedemodulation LSI 20. In a RAM 28, the data from the CPU 26 is stored ata rate of one packet per 18 msec. The RAM 28 is operated as a buffer foroutputting data to an interface 30.

An address decoder 32 causes the interface 30 to output data when itdetects that the CPU 26 gains access to the personal computer 101. Acontroller 34 outputs data to the personal computer 101 upon receipt ofthe data (data of a layer 3) outputted from the interface 30. At thetime of activating the FM multiplex broadcasting receiver, thecontroller 34 achieves initialization between the interfaces 30 and 38on the basis of data stored in the ROM 35.

A CPU 40 in the personal computer 101 receives the packet data (data ofa layer 3) outputted from the sub-carrier data decoding unit 15 throughthe interface 38. The CPU 40 extracts a data block from the receivedpacket data, reconstructs a data group from the data block, and subjectsthe data group to error detection. Further, the CPU 40 extracts a prefixcorresponding to a data block at the head of each of data groups fromthe received packet data, and stores the prefix in the storage device44.

The reconstructed data groups are successively stored in units of pagesin the storage device 44 for each program. The CPU 40 selectspredetermined page data, and outputs the page data to the display unit42. The display unit 42 outputs corresponding character information andfigure information on the basis of the sent page data.

The CPU 40 performs data retaining processing when a command to retain areceived program is entered by a user.

FIG. 5 shows the procedure for the data retaining processing by the CPU40.

Data group data in a layer 4 and the prefix corresponding to the datablock at the head of each of the data groups which are stored in thestorage device 44 are first acquired (step 1).

A prefix corresponding to each of data blocks constituting the acquireddata group data is then reproduced on the basis of the prefixcorresponding to the data block at the head of each of the data groupswhich is acquired in the step 1, and a prefix corresponding to each ofdata blocks included in the layer 4 is added thereto (step 2). Data of alayer 3 is thus produced.

The obtained data of the layer 3 is retained in the storage device 44 asversatile recording and reproducing data (step 3). When such processingis terminated with respect to all programs (step 4), the current dataretaining processing is terminated.

According to the above-mentioned embodiment, the data of the layer 3 canbe stored as versatile recording and reproducing data. In various typesof applications for reproducing FM multiplex broadcasting, therefore,the original programs at the time of receiving can be faithfullyreproduced from the retained data.

What is claimed is:
 1. An FM multiplex broadcasting receiver comprising:means for storing in first storage means a prefix corresponding to adata block at the head of each of data groups of a received FM multiplexbroadcast program and data of a first layer of the received FM multiplexbroadcast program; an input device for entering a data retentioncommand; and means for producing data of a second layer based on theprefix and the data of the first layer which are stored in said firststorage means when the data retention command is entered and forretaining in a second storage means the produced data of the secondlayer as a recording and reproducing data.
 2. The FM multiplexbroadcasting receiver according to claim 1, wherein said first storagemeans and said second storage means are the same storage device.
 3. Amethod of retaining received data in an FM multiplex broadcastingreceiver, comprising the steps of: storing in first storage means aprefix corresponding to a data block at the head of each a plurality ofdata groups of a received FM multiplex broadcast program and data of afirst layer of the received FM multiplex broadcast program; andproducing data of a second layer based on the prefix and the data of thefirst layer which are stored in said first storage means when a dataretention command is entered and retaining in a second storage means theproduced data of the second layer as a recording and reproducing data.4. The method according to claim 3 wherein said first storage means andsaid second storage means are the same storage device.